Nuclear Magnetic Resonance Imaging or MRI is a non invasive imaging technique which exploits the inherent magnetic field produced by nuclei of atoms with a nonzero spin. Since hydrogen is the most abundant atom, it forms the basis of NMR imaging techniques. The transparency of many materials to RF irradiation coupled with the access to a large variety of contrast parameters and the non-destructiveness of the method may make it highly useful in materials imaging. In a number of situations... Show moreNuclear Magnetic Resonance Imaging or MRI is a non invasive imaging technique which exploits the inherent magnetic field produced by nuclei of atoms with a nonzero spin. Since hydrogen is the most abundant atom, it forms the basis of NMR imaging techniques. The transparency of many materials to RF irradiation coupled with the access to a large variety of contrast parameters and the non-destructiveness of the method may make it highly useful in materials imaging. In a number of situations there is a critical need to evaluate the distribution of small amounts of water adsorbed throughout a solid sample. One of these pertains to Spray-On Foam Insulation (SOFI), a thermal insulation material used on liquid hydrogen and oxygen tanks on space shuttles. The basic components of an NMR spectrometer are the magnet, amplifiers, transceiver and imaging coils. In MRI, imaging coils are radio-frequency coils that serve two purposes: the excitation of nuclear spins and the detection of nuclear precession. This thesis aims to successfully design a RF coil for 1H imaging of foam and the water trapped within it. The single turn solenoid is probably the most simple and efficient RF coil design. This type was selected as it has high sensitivity and uniform homogeneity throughout the volume of the coil. The coil has been optimized in terms of dimension, feasibility, strategies for tuning and matching and performance. Show less

Date Issued

2011

Identifier

FSU_migr_etd-1806

Format

Thesis

Title

2-Channel Low Power Broadband Transmit/Receive Switch and 720 Mhz High Power Narrow Pass Band Filter.

Nuclear magnetic resonance (NMR) is an important tool used to study the atomic or molecular properties of nuclei by exploiting its magnetic properties. A spectrometer is an integral element of an NMR system which consists of a RF transmitter, receiver, amplifier, temperature controller, transmit/receive switch, filter, etc. A transmit/receive switch is used to toggle between transmission and reception modes of the resonant coil in the RF probe. The following thesis consists of the design and... Show moreNuclear magnetic resonance (NMR) is an important tool used to study the atomic or molecular properties of nuclei by exploiting its magnetic properties. A spectrometer is an integral element of an NMR system which consists of a RF transmitter, receiver, amplifier, temperature controller, transmit/receive switch, filter, etc. A transmit/receive switch is used to toggle between transmission and reception modes of the resonant coil in the RF probe. The following thesis consists of the design and construction of one such T/R switch that is used to perform NMR field mapping of resistive magnets in the presence of temporal field fluctuations. This low power T/R switch consisting of two receive channels and a common transmitter is designed to operate over a wide range of proton (1H) NMR frequencies i.e., 200 MHz to 1600 MHz and can handle up to 1 watt power. It uses a micro strip transmission line design utilizing low power surface mount switches, splitters and drop-in preamps. The other part of this thesis deals with the design of a band pass filter tuned at 720 MHz. In multi nuclear pulsed NMR experiments, a high power band pass filter is used to improve the isolation between the channels of the spectrometer and screen out the other frequencies and noise signals from the system. The filter is designed using two semi-rigid coaxial cables grounded at their ends. This design is evaluated for its performance (insertion loss and reflection coefficient). The construction challenges have also been discussed. The filter is capable of handling a maximum RF input of 1 kilowatt rms power, has a 3dB bandwidth of 40 MHz and produces an insertion loss as low as 1dB. Show less

A Power Hardware-in-the-Loop (PHIL) simulation should be accurate to truly reflect the behavior of the systems under test. However, a PHIL simulation may result in errors or even instability due to imperfections (e.g., time delay, noise injection, phase lag, limited bandwidth) in the power interface. This issue is especially problematic in high power applications. Additionally, it is usually difficult to determine the accuracy of simulation results because there is no reference available.... Show moreA Power Hardware-in-the-Loop (PHIL) simulation should be accurate to truly reflect the behavior of the systems under test. However, a PHIL simulation may result in errors or even instability due to imperfections (e.g., time delay, noise injection, phase lag, limited bandwidth) in the power interface. This issue is especially problematic in high power applications. Additionally, it is usually difficult to determine the accuracy of simulation results because there is no reference available. Consequently, a method is needed to evaluate the accuracy of PHIL simulations. In this thesis, an effective method for evaluating the accuracy of PHIL simulations is proposed. This method provides a means to justify the result of a PHIL simulation analytically and quantitatively instead of empirically. In the derivation of the method, it is also found that the magnitude of the system's open loop transfer function can be taken as one of the most important performance indices for evaluating different interface algorithms. This conclusion is significantly useful for the selection of the optimal interface algorithms and for the future design of advanced interface algorithms. Although the proposed method is derived based on linear system analysis, it is shown to be effective for many nonlinear systems also. Simulations and experiments are performed for the purpose of validation. Limitations of the method are also discussed. For cases where the proposed method fails to be effective, a simulation-only method is proposed and explained as the future work. Show less

Motion control of robot manipulators is typically accomplished by sensing and regulating the positions of the joint actuators to cause the end-effector to follow a programmed trajectory. Unfortunately, position control schemes usually fail for tasks that require significant physical interaction between the robot and a workpiece. This restriction severely limits the scope of work that robots are able to do. A solution to this problem is to incorporate some form of compliance into the... Show moreMotion control of robot manipulators is typically accomplished by sensing and regulating the positions of the joint actuators to cause the end-effector to follow a programmed trajectory. Unfortunately, position control schemes usually fail for tasks that require significant physical interaction between the robot and a workpiece. This restriction severely limits the scope of work that robots are able to do. A solution to this problem is to incorporate some form of compliance into the manipulator to compensate for positioning errors. Researchers have been focused on two principal methods of achieving manipulator compliance -- passive mechanism synthesis and active force control -- both of which have advantages and disadvantages. In this thesis, recent advances in passive mechanism synthesis algorithms are presented, and highlighted by two new algorithms that were developed during this research. New results in stiffness matrix analysis are presented on the bounds of the stiffness constants and relationship between the diagonal components and eigenvalues of a symmetric matrix. Active force control is explored, and stability problems are analyzed. Previous efforts at combining active and passive interaction control are assessed, and an improved method is proposed to simultaneously provide a simple, compact, passive mechanism with an active force control scheme to obtain a compliant manipulator with desirable characteristics for interaction control. Show less

Filtering data in real-time requires dedicated hardware to meet demanding time requirements. If the statistics of the signal are not known, then adaptive filtering algorithms can be implemented to estimate the signals statistics iteratively. Modern field programmable gate arrays (FPGAs) include the resources needed to design efficient filtering structures. Furthermore, some manufacturers now include complete microprocessors within the FPGA fabric. This mix of hardware and embedded software on... Show moreFiltering data in real-time requires dedicated hardware to meet demanding time requirements. If the statistics of the signal are not known, then adaptive filtering algorithms can be implemented to estimate the signals statistics iteratively. Modern field programmable gate arrays (FPGAs) include the resources needed to design efficient filtering structures. Furthermore, some manufacturers now include complete microprocessors within the FPGA fabric. This mix of hardware and embedded software on a single chip is ideal for fast filter structures with arithmetic intensive adaptive algorithms. This thesis aims to combine efficient filter structures with optimized code to create a System-on-chip (SoC) solution for various adaptive filtering problems. Several different adaptive algorithms have been coded in VHDL as well as in C for the PowerPC 405 microprocessor. The designs are evaluated in terms of design time, filter throughput, hardware resources, and power consumption. Show less

Modal based traditional Structural Health Monitoring techniques are limited because of several factors – including a poorly-formed aggregate system model, very low SNR, and unrealistic boundary conditions. Moreover, global techniques often rely on modal damage indicators that are not sensitive to localized damage. In this dissertation, the author proposes a new Damage Detection technique that addresses the space-frequency localization of damage artifacts in a reference and no-reference... Show moreModal based traditional Structural Health Monitoring techniques are limited because of several factors – including a poorly-formed aggregate system model, very low SNR, and unrealistic boundary conditions. Moreover, global techniques often rely on modal damage indicators that are not sensitive to localized damage. In this dissertation, the author proposes a new Damage Detection technique that addresses the space-frequency localization of damage artifacts in a reference and no-reference framework. For the first situation of referenced damage detection, the author employs the use of compactly supported subband space/frequency and time/frequency analysis using local vibration characteristics, overcoming the signal to noise ration problem with a nearfield adaptive beamformer filter bank. The beamformer filter bank operates on the subband space and provides accurate spatial selectivity and high signal to noise ratio for any given scan direction. Subband analysis is performed using wavelet packets and Daubechies mother wavelets. The system is simulated using a one dimensional Finite Element model of a simply supported beam with simple constraints as a good approximation of a real situation. The local damage is simulated as a reduction of the Young's modulus over a selected group of elements. The Damage Detection is performed using as a damage feature the subband energy for any given scan direction and for each subband center frequency. The energy signature for every location/frequency is compared to the energy signature obtained for the equivalent undamaged structure. The obtained results are validated against the analysis obtained before the beamforming stage, and the algorithm localizes the damage in areas of high probability around the direction of the simulated discontinuity. Moreover, the proposed technique shows a very high accuracy and it is able to detect variations on the structure parameters as low as 1%, with a signal near the noise level. For the second situation of Damage Detection performed without an undamaged reference for the analysis, the author proposes a new statistical method based on the density estimation of the vibration signal. This technique is based in the Gaussian Mixture estimation of the probability density function of the vibration signal, using a greedy EM approach with a new model order selection criteria. This model order is based on global measurement on the cumulative density function as well as on local measurement on density indicators, such as the Kullback-Leibler divergence and the estimated Correlation Coefficient. The technique is used to estimate the density of time domain signal and frequency domain signal. As damage indicators, the technique uses the first two principal components from measurements of standard deviation, kurtosis, skewness and entropy on the estimated density. The obtained damage indicators perform better in frequency domain and damage as low as 30% can be detected in a noisy environment. Show less

The growing concerns for environment, increasing demand growth and threat of energy shortage continue to accentuate the request of upgrading the traditional power grid. Smart grid is envisioned to take advantage of all available modern technologies in transforming the current grid to one that functions more intelligently to facilitate integration of renewable energy source and energy storages, to provide higher quality of service and so on. Solid State Transformer (SST) is an essential... Show moreThe growing concerns for environment, increasing demand growth and threat of energy shortage continue to accentuate the request of upgrading the traditional power grid. Smart grid is envisioned to take advantage of all available modern technologies in transforming the current grid to one that functions more intelligently to facilitate integration of renewable energy source and energy storages, to provide higher quality of service and so on. Solid State Transformer (SST) is an essential technology for integration of the distributed energy resources, distributed energy storage, and intelligent loads. It has the advantages of its reduced size and weight/volume with high frequency transformer, high power density, and good power quality. Comparing to other SST topologies, the three-stage SST is more promising due to its advantages to provide power factor correction, reactive power compensation and an additional regulated DC bus The bi-directional dc-dc converter is the key stage in the three-stage SST topology configuration since it provides not only the high frequency galvanic isolation, but also determines the system overall efficiency and power density. Therefore, the dc-dc converter promising dynamic performance is the key requirement for the three-stage SST. Currently, few literatures research on the three-stage SST system dynamics, especially for the soft start-up issue. Three-stage SST requires a delicate start-up control scheme because of three conversion stages and high frequency transformer. The major challenge of researching start-up issue is how to develop a theoretical analysis strategy to study different schemes. The thesis researches this issue by formulating the transformer instaneous peak current with respects to all the key impact factors. As a result, different schemes can be investigated by using a unified formula. Moreover, a new soft start-up scheme is proposed with the minimized transformer current response. The thorough analysis of the DC-DC converter transformer current during the three-stage SST start-up and the proposed start-up scheme is described in details in chapter 2. Fuel cell is an important renewable energy source of distributed energy storage device for new mobile applications and power generation system since it offers high efficiency, low emissions of regulated pollutants and excellent part-load performance. The major challenge for fuel cell power conditioning system is to limit the fuel cell low-frequency current ripple resulted from the inverter load. The traditional solution is to adopt the large electrolytic capacitor as the energy buffer. However, the large-sized electrolytic capacitors will decrease the system lifetime as well as increase the system volume and cost. A new current-fed phase-shift controlled dc-dc converter based fuel cell power conditioning system is proposed in this thesis with low-frequency ripple free input current using a control-oriented power pulsation decoupling control scheme. Without adding any extra components, the proposed fuel cell converter realizes the power pulsation decoupling function so as to reduce the dc bus capacitor, thus allowing for choosing long lifetime film capacitor to replace the bulky electrolytic capacitor. The proposed decoupling control design is based on the system small-signal average model. The detailed system operation analysis and proposed decoupling control design guideline is presented in chapter 3. The chapter 4 summarizes the dissertation work. Show less

Robot manipulators can be used to navigate and perform tasks in unstructured and hazardous environments where human safety is a primary concern. For example, they are used for nuclear waste disposal, space exploration, nuclear power industry, military surveillance, etc. A number of such robot manipulators are being used but the concern is that these robots should be able to complete their critical tasks in the event of failures that they encounter working in such environments. One of the most... Show moreRobot manipulators can be used to navigate and perform tasks in unstructured and hazardous environments where human safety is a primary concern. For example, they are used for nuclear waste disposal, space exploration, nuclear power industry, military surveillance, etc. A number of such robot manipulators are being used but the concern is that these robots should be able to complete their critical tasks in the event of failures that they encounter working in such environments. One of the most common failures of field robots is an actuator failure. This type of failure affects the joints of the robots inducing failures like locked-joint failures and free-swinging joint failures. To design a fault tolerant system the robot has to rely on the incorporation of redundancy into its system. This redundancy takes several forms: sensor redundancy, analytical redundancy, and kinematic redundancy. This work focuses on using kinematic redundancy to deal with the issue of multiple locked-joint failures in the robotic systems. The goal of this work was to analyze and design fault-tolerant manipulators. The robots designed are able to finish their required task in spite of a failure in one or more of its joints. In order to design optimally fault tolerant manipulators, it is necessary to quantify fault tolerance. The approach taken here was to define fault tolerance in terms of a suitable objective function based on the robot's manipulator Jacobian. In the case of the relative manipulability index, local fault tolerance is characterized by the null space of the manipulator Jacobian. Since the null space can be used to identify locally fault tolerant manipulator configurations, one goal of this work was to develop procedures for designing fault tolerant manipulators based on obtaining a suitable null space for the manipulator Jacobian. In this work, optimally fault tolerant serial manipulators are designed that are fault tolerant to two locked-joint failures simultaneously. Furthermore, the symmetry of the manipulators is studied using positional and orientational Jacobians; and examples are presented for condition number and dynamic manipulability index to study the behavior of different fault tolerance measures. Lastly, a methodology for designing an optimally fault tolerant 4-DOF spherical wrist type mechanism was presented. It was shown that the orientational Jacobian must have a certain form for the manipulator to have the best possible relative manipulability index value. An optimal configuration along with the corresponding DH parameters was presented. Furthermore, it was pointed out that isotropic configurations of a 4-DOF spherical wrist type mechanism are fault tolerant and optimal in the sense that they have the largest possible manipulability index prior to a failure. An example of an orientational Jacobian was presented for a 6-DOF spherical wrist that is equally fault tolerant for any two joint failures. Show less

Date Issued

2012

Identifier

FSU_migr_etd-5433

Format

Thesis

Title

Analysis and Implementation of Grid-Connected Solar PV with Harmonic Compensation.

A grid-connected photovoltaic (PV) system with the functionality of harmonic compensation is introduced in this thesis. Based on this, a test bed is built up to validate the practicability of the proposed scheme. Increasing interest and investment in renewable energy give rise to rapid development of high penetration solar energy. There are multiple ways to interface PV arrays with the power grid. The topology of a multi-string two-stage PV module with a centralized inverter is developed in... Show moreA grid-connected photovoltaic (PV) system with the functionality of harmonic compensation is introduced in this thesis. Based on this, a test bed is built up to validate the practicability of the proposed scheme. Increasing interest and investment in renewable energy give rise to rapid development of high penetration solar energy. There are multiple ways to interface PV arrays with the power grid. The topology of a multi-string two-stage PV module with a centralized inverter is developed in the thesis, which is more suitable for medium power applications. However, the output of solar arrays varies due to change of solar irradiation and weather conditions. Therefore, the maximum power point tracking algorithm is implemented in DC/DC converter to enable PV arrays to operate at maximum power point. The incremental conductance algorithm is employed to control the boost converter. Then the central inverter is controlled by decoupled current control algorithm and interfaced with the utility grid via the distribution network. Besides, the current control of the inverter is independent of maximum power point control of the DC/DC converter. Finally, system performance and transient responses are analyzed under the disturbance conditions. And system stability is evaluated when solar irradiation change or system fault happens. The system is simulated in MATLAB. More and more use of static power converter and switched mode power supplies injects harmonic current into the power system. It's advisable that PV can be controlled to compensate the harmonic current as well as supply the active power. The harmonic current is extracted by using time-domain current detection method, which is much easier to implement and doesn't need any transformation comparing with the instantaneous power theory method. The system simulation is accomplished and validated by using PSCAD/EMTDC. Meanwhile, experimental test bed is also established to verify the proposed algorithm. Eventually, the total harmonic distortion (THD) of the grid current after compensation is analyzed and compared with the standard of IEEE 519-1992. Show less

A robust and computationally efficient Monte-Carlo based technique is developed to analyze the magnetic aftereffect and noise passage phenomena in magnetic hysteretic systems by using phenomenological models of hysteresis. The technique is universal and can be applied to model the aftereffect and noise passage phenomena in the framework of both scalar and vector models of hysteresis. Using this technique, we analyze a variety of magnetic viscosity phenomena. Numerical results related to the... Show moreA robust and computationally efficient Monte-Carlo based technique is developed to analyze the magnetic aftereffect and noise passage phenomena in magnetic hysteretic systems by using phenomenological models of hysteresis. The technique is universal and can be applied to model the aftereffect and noise passage phenomena in the framework of both scalar and vector models of hysteresis. Using this technique, we analyze a variety of magnetic viscosity phenomena. Numerical results related to the decay of the magnetization as a function of time as well as to the viscosity coefficient are presented. It is shown that a logt (logarithmic time) - type dependence of the average value of the magnetization can be predicted qualitatively in the framework of phenomenological models of hysteresis, such as the Preisach, Energetic, Jiles-Atherton, and Hodgdon models. The basic assumption of the techniques developed in this dissertation is that the total applied field is equal to the external applied field plus a random perturbation field. The total magnetic field is used as input in the scalar or vector models of hysteresis (vector models of hysteresis are defined in this dissertation as a superposition of scalar models of hysteresis distributed along all possible spatial directions). A statistical approach is developed to compute the average value and direction of the magnetization vector as a function of time. Whereas in the case of isotropic materials the magnetization vector usually moves on a straight line oriented towards the direction of the applied field, in the case of anisotropic materials the magnetization vector can switch from one easy axis to another and cross the direction of the applied field. It is shown that, depending on the initial hysteretic state, the trajectory of the magnetization vector can deviate substantially from the straight line, which is a pure vectorial relaxation effect. The vectorial properties of magnetic viscosity and data collapse phenomena are also investigated. The definition of the viscosity coefficient, which has been traditionally used to model aftereffect phenomena in scalar magnetic systems, is generalized in order to describe three dimensional systems, where both the direction and the magnitude of the magnetization vector can change in time. Using this generalization of the vector viscosity coefficient, we have analyzed data collapse phenomena in vectorial magnetization processes. It was found that the traditional bell-shaped curves of the scalar viscosity coefficient as a function of the applied field can have one or more maxima in the case of vectorial systems. The data collapse phenomena seem to apply to simple magnetization processes (such as first-order rotational reversal curves); however, it cannot be generalized to more complex magnetization processes because of the relatively complicated magnetization dynamics. In the final part of this dissertation we present a statistical technique based on Monte-Carlo simulations, which we developed to compute the spectral densities of the output variable in phenomenological models of hysteresis. The input signal is described by an Ornstein-Uhlenbeck process and the magnetization is computed by using various phenomenological models of hysteresis: the Energetic, Jiles-Atherton, and Preisach models. General qualitative features of these spectral densities are examined and their dependence on various parameters is discussed. For values of the diffusion coefficient near and smaller than the coercive field, the output spectra deviate significantly from the Lorentzian shape, characteristic to the input process. The intrinsic differences between the transcendental, differential, and integral modeling of hysteresis yield significantly different spectra at low frequency region, which reflect the long-time correlation behavior. Show less

The stochastic nature of ion implantation and diffusion processes induces variations of random doping concentration, which result in the fluctuations of the intrinsic parameters of semiconductor devices. The fluctuations of intrinsic parameters become especially significant when the devices are scaled down, particularly when the spatial scale of random dopants variations becomes comparable with the geometric dimensions of device. In the thesis, the fluctuation of threshold voltage induced by... Show moreThe stochastic nature of ion implantation and diffusion processes induces variations of random doping concentration, which result in the fluctuations of the intrinsic parameters of semiconductor devices. The fluctuations of intrinsic parameters become especially significant when the devices are scaled down, particularly when the spatial scale of random dopants variations becomes comparable with the geometric dimensions of device. In the thesis, the fluctuation of threshold voltage induced by random doping in metal-oxide-semiconductor field-effect-transistors (MOSFETs) is analyzed by using a simple technique based on the solution of the two- dimension and three-dimension nonlinear Poisson equation. The two-dimension nonlinear Poisson equation is solved by solving the Jacobian matrix using Newton iteration technique. The three-dimension nonlinear Poisson equation is solved by a more efficient iterative method. This iterative method converges for any initial guess and can be implemented on computers with small memories. Both methods are both implemented in the C++ programming language. Sample simulation results are obtained and compared with the analytical results. Show less

This thesis examines security threats facing wireless networks and the effectiveness of security protocols deployed to combat these threats. The thesis will base its study on Wireless Local Area Network (WLAN) as defined by IEEE standards 802.11a/b/g/n. Features of each WLAN Security protocol, from WEP, WPA and IEEE 802.11i will be analyzed and the effectiveness of each protocol in ensuring data integrity, data confidentiality, and network availability will be presented. To allow mobility of... Show moreThis thesis examines security threats facing wireless networks and the effectiveness of security protocols deployed to combat these threats. The thesis will base its study on Wireless Local Area Network (WLAN) as defined by IEEE standards 802.11a/b/g/n. Features of each WLAN Security protocol, from WEP, WPA and IEEE 802.11i will be analyzed and the effectiveness of each protocol in ensuring data integrity, data confidentiality, and network availability will be presented. To allow mobility of users while ensuring network services are received at an acceptable quality level, fast handovers of client device from one Access Point (AP) to another are necessary. Mainly probing process, in which a client device looks for a proper AP to associate with, and the authentication process cause Handover delays. This thesis provides an analysis of authentication delay resulting from the use of different security protocols. A mathematical model was developed and used to calculate the authentication delay. The results obtained show that the largest delay is experienced with the 802.11i security protocol. In a network where frequent handovers of a client device are required from one Access point to another; the large latencies may lead to poor Quality of Service (QoS) or even interruption of real-time and interactive network services such as Voice Over Internet Protocol (VOIP). Show less

Date Issued

2007

Identifier

FSU_migr_etd-2372

Format

Thesis

Title

Analysis, Modeling and Simulation of Optimal Power Tracking of Multiple-Modules of Paralleled Solar Cell Systems.

Distributed and renewable energy generation (DG) offers great potential in meeting future global energy requirements. Distributed generation consists of small to medium size generators cited close to the customer and spread across a power system. The production of power from renewable energies will lead to a significant reduction in the rate of environmental pollution in comparison with the production by fossil fuels, thus gaining renewed attention due to advances in technology, environmental... Show moreDistributed and renewable energy generation (DG) offers great potential in meeting future global energy requirements. Distributed generation consists of small to medium size generators cited close to the customer and spread across a power system. The production of power from renewable energies will lead to a significant reduction in the rate of environmental pollution in comparison with the production by fossil fuels, thus gaining renewed attention due to advances in technology, environmental concerns and a growing energy demand. Photovoltaic systems in particular have great potential when compared to other renewable energies. The goals of this thesis are to perform a systematic analysis, modeling and evaluation of the key subsystems or components of a multiple-source renewable energy generation system and to develop an optimal tracking and control strategy. It is desirable to achieve maximum power output at a minimum cost under various operating conditions. Show less

Date Issued

2006

Identifier

FSU_migr_etd-2288

Format

Thesis

Title

Analysis, Simulation and DSP Based Implementation of Asymmetric Three-Level Single-Phase Inverter in Solar Power System.

Switching-mode single-phase DC-AC inverters have been widely used in many applications such as AC motor drivers and uninterrupted power supply systems. Among various control techniques, pulse-width-modulation (PWM) is the most effective one generally used to regulate the magnitude as well as frequency of the converter's output voltage. In this thesis, an open-loop asymmetric three-level inverter with a modified PWM approach is proposed. This novel topology with the modified PWM approach has... Show moreSwitching-mode single-phase DC-AC inverters have been widely used in many applications such as AC motor drivers and uninterrupted power supply systems. Among various control techniques, pulse-width-modulation (PWM) is the most effective one generally used to regulate the magnitude as well as frequency of the converter's output voltage. In this thesis, an open-loop asymmetric three-level inverter with a modified PWM approach is proposed. This novel topology with the modified PWM approach has advantages of smaller device voltage, less harmonics and power loss, and more flexible device selection, compared with conventional H-bridge inverter and NPC inverter. Theoretical analysis is completed; digital simulation is conducted to verify the theoretical analysis. Experimental implementation base on DSP is also performed and the results are demonstrated. Moreover, this inverter is applied in a three-arm solar power system. The theoretical analysis and digital simulation for the whole system are also presented. Show less

This dissertation addresses the synthesis of antenna arrays using the Cross-Entropy (CE) method, marking the first application of the CE method for solving electromagnetic optimization problems. The CE method is a general stochastic optimization technique for solving both continuous and discrete multi-extremal, multi-objective optimization problems. The CE method is an adaptive importance sampling derived from an associated stochastic problem (ASP) for estimating the probability of a rare... Show moreThis dissertation addresses the synthesis of antenna arrays using the Cross-Entropy (CE) method, marking the first application of the CE method for solving electromagnetic optimization problems. The CE method is a general stochastic optimization technique for solving both continuous and discrete multi-extremal, multi-objective optimization problems. The CE method is an adaptive importance sampling derived from an associated stochastic problem (ASP) for estimating the probability of a rare-event occurrence. The estimation of this probability is determined using a log-likelihood estimator governed by a parameterized probability distribution. The CE method adaptively estimates the parameters of the probability distribution to produce a random variable solution in the neighborhood of the globally best outcome by minimizing cross entropy. In this work, single and multi-objective optimization using both continuous and combinatorial forms of the CE method are performed to shape the sidelobe power, mainlobe beamwidth, null depths and locations as well as number of active elements of linear array antennas by controlling the spacings and complex array excitations of each element in the array. Specifically, aperiodic arrays are designed through both non-uniform element spacings and thinning active array elements, while phased array antennas are designed by controlling the complex excitation applied to each element of the array. The performance of the CE method is demonstrated by considering different scenarios adopted from literature addressing more popular stochastic optimization techniques such as the Genetic Algorithm (GA) or Particle Swarm Optimization. The primary technical contributions of this dissertation are the simulation results computed using the Cross Entropy method for the different scenarios adopted from literature. Cursory comparisons are made to the results from the literature, but the overall goal of this work is to expose the tendencies of the Cross Entropy method for array synthesis problems and help the reader to make an educated decision when considering the Cross Entropy method for their own problems. Overall, the CE method is a competitive alternative to these more popular techniques, possessing attractive convergence properties, but requiring larger population sizes. Show less

Date Issued

2008

Identifier

FSU_migr_etd-3444

Format

Thesis

Title

Application of an Intelligent Tuning Algorithm for Three-Level NPC Rectifier for Shipboard Power Distribution.

The demand for high-voltage and high-power power electronics devices, especially for the next generation electrical ship system, has increased rapidly these years. The three-phase three-level neutral point clamped (NPC) rectifier attracts more and more engineers' attention due to it has many advantages: sinusoidal input current which contains low harmonics, unity power factor, bidirectional power flow, low voltage and switching loss for each switch and so on. It could potentially provide DC... Show moreThe demand for high-voltage and high-power power electronics devices, especially for the next generation electrical ship system, has increased rapidly these years. The three-phase three-level neutral point clamped (NPC) rectifier attracts more and more engineers' attention due to it has many advantages: sinusoidal input current which contains low harmonics, unity power factor, bidirectional power flow, low voltage and switching loss for each switch and so on. It could potentially provide DC power to medium voltage DC distribution system on ships. A NPC rectifier system is introduced in this thesis and the hardware test bed for validating is built successfully. Base on the topology of NPC rectifier, the PWM math model in ABC stationary frame is set up first. In order to obtain constant control variables as in DC motor control, the NPC rectifier PWM math model in DQ0 reference frame is built. And then for design the control loop, the NPC rectifier average models are developed in both ABC stationary frame and DQ0 reference frame. Three-level SVM is used for achieving sinusoidal input current, lower current THD and lower switching loss. Neutral point voltage balance problem is an inherent problem of three-level PWM rectifier. Without neutral point voltage control, the harmonic components of input current will greatly increase, and the DC-link capacitors and the switching devices may probably be destroyed. The influences of every switching state on neutral-point are analyzed and the small-vector is actively utilized to solve the neutral point balance problem. When to design the PI controller gains, the classic Nichols and Ziegler rules and the NPC system responses to this tuning algorithm are showed firstly. Further optimization for the system PI controller gains, which base on Particle Swarm Optimization (PSO), is used and the system responses are compared to the classic Nichols and Ziegler rules'. Hardware data validate the improvement of PSO contributes to the NPC system. A NPC rectifier real-time Controller-hardware-in-the-loop (CHIL) test is completed before the real hardware experiment since it could de-risk the controller for hardware experiment. The real-time simulation is compared to the hardware experiment, the CHIL methodology is approved. Show less

Systems with critical functionality and are prone to damage due to excessive stress level from operation conditions and working environment requires health monitoring. Condition or health monitoring involves acquiring data that can be analyzed to determine the occurrence of faults, determine the type of fault, determine the severity of a fault and determine when the next fault would occur. This research has considered new fault analysis techniques for rotating electrical machines using... Show moreSystems with critical functionality and are prone to damage due to excessive stress level from operation conditions and working environment requires health monitoring. Condition or health monitoring involves acquiring data that can be analyzed to determine the occurrence of faults, determine the type of fault, determine the severity of a fault and determine when the next fault would occur. This research has considered new fault analysis techniques for rotating electrical machines using Artificial Intelligence (AI) techniques. The analysis has been carried out in three sections: fault diagnosis, fault detection and fault prognosis. By way of fault diagnosis, Finite Element Analysis (FEA) has been used to model different faults in a Permanent Magnet Synchronous Machine (PMSM) which has been analyzed by way of classification using five Artificial Intelligence Techniques. The original large dimensional dataset is first used in the classification process and the different fault classifiers compared based on their performance using different fault classifiers from the FEA model. The dimensions of the dataset are reduced, using four different manifold reduction techniques. Manifold reduction is carried out to reduce the computational burden of fault classification on high dimensionality data. Two new techniques for fault detection using AI is presented and applied to PMSMs by way of computer simulations and experimental data from an actual PMSM. One technique called the Peak-to-Peak technique uses an Artificial Neural Network (ANN) trained using PSO and can distinguish short circuit faults from loading transients. In the second method, called Turn-to-Turn method, the zero current components is used to determine the number of shorted turns in the stator windings using an ANN trained using the Extended Kalman Filter (EKF) method. Finally a new method of determining the time-to-breakdown of insulation systems is presented as a fault prognosis approach. Also a new micro simulation model is presented for simulating the breakdown of dielectric materials. The new prognostics method is based on a macro model developed in conjunction with ANNs. The prognosis approach is based on associating the breakdown characteristics of dielectrics to Partial Discharge (PD) that take place during dielectric breakdown. Show less

Date Issued

2013

Identifier

FSU_migr_etd-8713

Format

Thesis

Title

Applications of Compressive Sampling for Reconstruction in Side-Scan Sonar Imagery.

The Nyquist-Shannon sampling theorem states that in order to reconstruct a compressed image, the number of samples needed must match the desired resolution. In other words the signal must be sampled at a rate at least twice the largest bandwidth in order to avoid aliasing. However it is possible and mathematically proven that compressive sampling (CS) can defy this theorem. The basic idea behind compressive sampling is to transform the image or signal into a suitable basis function and then... Show moreThe Nyquist-Shannon sampling theorem states that in order to reconstruct a compressed image, the number of samples needed must match the desired resolution. In other words the signal must be sampled at a rate at least twice the largest bandwidth in order to avoid aliasing. However it is possible and mathematically proven that compressive sampling (CS) can defy this theorem. The basic idea behind compressive sampling is to transform the image or signal into a suitable basis function and then carry out only the important expansion coefficients. CS is incomplete without a suitable method for reconstruction. Theoretically, reconstruction relies on the minimization and optimization techniques to solve this complex almost NP-complete problem. There are many paths to consider when compressing and reconstructing an image but these methods have remained untested and unclear on natural images, such as underwater sonar images. The majority of the research remains in the medical imaging area. In our proposed work, we test current methods of reconstruction versus an alternative optimization algorithm that has yet to be used in compressive sampling, specifically the cross entropy method. Our focused application is on maintaining pertinent information, such as mine-like objects or tumor-like areas, in Side-scan sonar (SSS) images, magnetic resonance imaging (MRI) and mammography, respectively. Currently the JPEG-2000, a multi-level discrete wavelet transform, is the industry standard in image compression but this post processing could be avoidable with compressive sampling. A more efficient process of compression during the sampling stage and post processing reconstruction for SSS images has remained untested. Hence the motivation is to test current and new methods on SSS images, along with medical images for a baseline. The proposed methods can be a competitive alternative to the industry standard of post processing using the wavelet based JPEG-2000 and JPEG on SSS images, MRI and mammography. The final proposed work introduces a new method to denoise SSS images. This method solves the popular Total Variation (TV) problem by splitting the energies of the l1 and l2-norms. The resulting image will have a higher resolution and, depending on the parameters chosen, will be smoother. Show less

This thesis presents and evaluates a bio-inspired vision system design to increase the depth field of a stereoscopic ranging imager. Two key attributes of the human vision system are leveraged in this design. The first attribute is image stabilization similar to the inner ear semi-circular canals and neck muscles. To accomplish this, an accelerometer and servos were used to stabilize the imager platform. The second human vision attribute used by the design is the ability to change the focal... Show moreThis thesis presents and evaluates a bio-inspired vision system design to increase the depth field of a stereoscopic ranging imager. Two key attributes of the human vision system are leveraged in this design. The first attribute is image stabilization similar to the inner ear semi-circular canals and neck muscles. To accomplish this, an accelerometer and servos were used to stabilize the imager platform. The second human vision attribute used by the design is the ability to change the focal vector. This is accomplished by a servo that tilts the imagers in unison and separate servos that enable each imager to pan independently. The performance metrics of depth field size and resolution of this method are compared to a system that has statically-mounted imagers and a fixed video platform. Show less

Date Issued

2011

Identifier

FSU_migr_etd-1562

Format

Thesis

Title

Birdcage Coils for MRI: In Vivo Imaging of 35-Chlorine and 1-Hydrogen Nuclei.

In this thesis, three different RF coils were investigated for their application in Magnetic Resonance Imaging (MRI). We developed transmit/receive birdcage volume coils since they provide better B1 field homogeneity than other coils. Coils were developed for in vivo imaging of chlorine and hydrogen nuclei. Chlorine is a low γ nucleus, therefore its sensitivity is very low. The high field of 21.1 T at NHMFL was exploited in order to obtain better signal strength from chlorine. Also, a... Show moreIn this thesis, three different RF coils were investigated for their application in Magnetic Resonance Imaging (MRI). We developed transmit/receive birdcage volume coils since they provide better B1 field homogeneity than other coils. Coils were developed for in vivo imaging of chlorine and hydrogen nuclei. Chlorine is a low γ nucleus, therefore its sensitivity is very low. The high field of 21.1 T at NHMFL was exploited in order to obtain better signal strength from chlorine. Also, a comparative study was conducted between the linear coil and the quadrature coil of chlorine. Quadrature excitation helps in increasing the RF power efficiency, and results in up to √2 improvement in signal-to-noise ratio. In this work, strategies are presented for tuning, matching and isolating the two ports. We developed a third coil for proton imaging which incorporated the sliding ring tuning mechanism. The principle of sliding ring is to provide distributed capacitance. This results in tuning across all legs which in turn helps to maintain the symmetry of the birdcage coil. The resonance and quality factor was measured for all the three coils when loaded with saline, oil and poly ethylene glycol (PEG) solutions. In vivo experiments were carried out in order to image phantoms and rats in the 21.1 T magnet. It was observed that the quadrature chlorine coil provided 1.18 times improvement in sensitivity when compared to the linear coil. The sliding ring coil for proton helped in preserving the symmetry; it offered better tuning range when compared to the fixed lumped element design. RF coils are critically important in the performance of MRI scanners. We believe that the studies conducted in this project are contributions toward obtaining better imaging systems. Show less

This paper investigates the stability issues in an islanded microgrid. A microgrid, once disconnected from the main grid, has to entirely depend on the Distributed Generators (DG), which are mostly intermittent renewable sources (e.g. PV, Wind Turbine etc.). This makes it necessary to achieve proper sharing of power, as it is not possible to supply the entire microgrid by a single source. Frequency and angle droop along with supplementary and adaptive control methods are analyzed and compared... Show moreThis paper investigates the stability issues in an islanded microgrid. A microgrid, once disconnected from the main grid, has to entirely depend on the Distributed Generators (DG), which are mostly intermittent renewable sources (e.g. PV, Wind Turbine etc.). This makes it necessary to achieve proper sharing of power, as it is not possible to supply the entire microgrid by a single source. Frequency and angle droop along with supplementary and adaptive control methods are analyzed and compared to identify the better method for accurate load sharing. However, the conventional droop methods, which are designed for inductive microgrids, allow an error in reactive power sharing when applied in a resistive microgrid. Therefore, a secondary control is proposed for improving the accuracy of reactive power sharing. The droop method alone is not enough in situations of severe power outages, like loss of a DG unit. Use of an Energy Storage System (e.g. Battery) is proposed to serve both as a storage unit for the intermittent sources and also to prevent voltage collapse by supplying the required voltage to the load bus. In addition to that, an advanced load shedding scheme is proposed to sustain the important loads, in times of extreme power crisis. Voltage unbalance caused by harmonic distortion, due to the presence of unbalanced/non-linear loads may result in voltage collapse. A selective harmonic compensation method along with local droop controller illustrates an effective way of restoring voltage balance, even with the harmonic polluted loads connected to the network. In addition to this, the role of a programmable resistance with shunt harmonic impedance (PR-SHI) in harmonic compensation is investigated in this paper. This method is shown to allow a reduced harmonic current and achieve an accurate sharing of the harmonic compensation effort among the DG units. Lastly, a scenario of excess generation, very uncommon to the conventional grid, has been discussed in this paper. Charging of battery unit and generation of heat energy, by using Smart Loads is proposed to be the most effective way of utilizing the excess generated power. This thesis presents a unique work of bringing together different control techniques used for stability of microgrid and analyzing and comparing them in order to find the best fit for each of the possible cases in an islanded microgrid. Lastly, it recommends solutions for each case. Show less

The ability to quantify device performance characteristics is a concern shared by developers, manufacturers, and consumers alike. From a subatomic perspective, the fluctuations found in repeated measurements can be attributed to the random nature of the charge carriers – the electrons. This limitation is also present in any receiver noise measurement set-up. The uncertainty of a noise measurement should be reported with the measurement, but assessing it can be problematic. The receiver system... Show moreThe ability to quantify device performance characteristics is a concern shared by developers, manufacturers, and consumers alike. From a subatomic perspective, the fluctuations found in repeated measurements can be attributed to the random nature of the charge carriers – the electrons. This limitation is also present in any receiver noise measurement set-up. The uncertainty of a noise measurement should be reported with the measurement, but assessing it can be problematic. The receiver system noise equation, which describes a measurement system, possesses non-linear parameter dependencies. Because of this, an intuitive or quantitative assessment of the measurement uncertainties would be very difficult, if not impossible, to obtain. This research work analyzes the measurement uncertainty inherent to a receiver noise measurement set-up utilizing Monte Carlo simulations. The algorithm used to assess the uncertainty incorporates a random number generator, a non-linear least squares fitting routine, and an uncertainty extraction routine. The random number generation depends on the behavior of noise sources; consequently, it produces either a normal or uniform distribution of data. Normalizing the generator allows the spread to be centered about a desired mean with a desired variance. The variance is a function of the underlying uncertainties associated with the test equipment employed. These values are given in the equipment specification sheets. The spread of real measurement data taken in a testing environment arises from perfectly uncorrelated, partially correlated, and perfectly correlated noise sources. The extreme cases (perfectly uncorrelated and perfectly correlated) are utilized to determine the effect of the erratic behavior of the charge carriers at the extremes. To simulate correlated noise sources, the random numbers are generated with the same random number generator. For the uncorrelated noise sources, the random numbers are generated by separate random processes. Once the random numbers are created, they are used to generate a spread of noise parameter simulated data. Due to the non-linear dependencies of these noise parameters, the effects of the random deviants on measurement uncertainty can not be predicted. An over-determined system of equations allows the receiver parameters of interest to be solved for. The over-determined system of equations can be created because one of the underlying noise parameters has multiple states. Over-determining the system allows for statistical smoothing of the data points. As mentioned previously, the noise parameters have non-linear dependencies and the system noise equation can not easily be transformed into a linear form. Consequently, a non-linear fitting routine is employed. The number of solutions the routine could find for one over-determined set of equations is endless, therefore the acceptable solutions are confined to values close to the true values – "true values" being a set of values actually measured in the testing environment. This confinement simply entails setting the value used as the initial guess for the fitting routine to that of the true value. Once a set of values is found for the receiver parameters, the process is repeated N times (N being the number of simulated data points desired). For each receiver parameter, there are N values that deviate about some mean value. The spread in values is a function of the underlying random process, but the behavior can not be predicted due to the non-linear dependencies. The only assumption that can be made is that the spread should exhibit a Gaussian distribution since all of the random data (except ambient temperature) is created based on this normal distribution. The overall uncertainty in the noise temperature for several devices is determined and compared with the value estimated for a simulated system. Several frequencies are selected for the analysis. The results show good agreement for calculations performed within either 1 or 2 standard deviations of the mean value for the hot and ambient loads. The estimated uncertainty for the simulated receiver system offers explanation as to why the cold load noise temperature measurement uncertainty diverges from the values found for the other DUTs. Show less

Currently over 50% of the world's population check their e-mails everyday. Collecting information from the Internet is a routine. In the early 21st century, wireless communication has become a hot topic in IT (Information Technology) and CT (Communication Technology), as evidenced by the growth of wireless technologies such as 3G, Wi-Fi and WiMax. 3G is a cellular technology developed in conjunction with the cellular phone network. Wi-Fi is a wireless local area network technology. WiMax is... Show moreCurrently over 50% of the world's population check their e-mails everyday. Collecting information from the Internet is a routine. In the early 21st century, wireless communication has become a hot topic in IT (Information Technology) and CT (Communication Technology), as evidenced by the growth of wireless technologies such as 3G, Wi-Fi and WiMax. 3G is a cellular technology developed in conjunction with the cellular phone network. Wi-Fi is a wireless local area network technology. WiMax is designed for the wireless metropolitan area network. Today, people not only want the fixed wireless access to the Internet, but also want the mobile wireless access as well. They want a ubiquitous connection, even when in a train, a cab, or the subway. This demand is resulting in increasing competition between the leading wireless technologies. 3G, Wi-Fi and WiMax all appear to have the potential to feed the demand, but still have issues that need to be addressed. The future direction of wireless Internet access is uncertain, including whether these three technologies will operate cooperatively or competitively. This thesis is going to predict the future direction by analysis of 3G, Wi-Fi and WiMax technologies and the evaluation of three wireless access case studies. This thesis will begin with an introduction to the history of Internet and will then continue with a discussion of the technical aspects of 3G, Wi-Fi and WiMax. After the technology introduction, this thesis will evaluate three current implementations of wireless Internet access as case studies to verify the capabilities of Wi-Fi and WiMax, and to discuss the feasibility of building a city-wide wireless network. Finally, a reasonable prediction of the future implementation of a city-wide wireless Internet structure will be presented. Show less

Date Issued

2007

Identifier

FSU_migr_etd-0701

Format

Thesis

Title

A Comparitive Study of Supervised and Unsupervised Learning Methods in Forecasting the U.S. 30-Year Treasury Bond Yield.

The prediction of any aspect of the future has always fascinated mankind because of the possible benefits of this knowledge, especially financial benefits. From year to year, many stockholders would like to be able to know if the price of their commodity will increase or decrease, and in turn this prediction may help them in the decision to buy more or sell what they currently have. It is widely known that the stock market is a volatile and complex entity which is affected by various factors... Show moreThe prediction of any aspect of the future has always fascinated mankind because of the possible benefits of this knowledge, especially financial benefits. From year to year, many stockholders would like to be able to know if the price of their commodity will increase or decrease, and in turn this prediction may help them in the decision to buy more or sell what they currently have. It is widely known that the stock market is a volatile and complex entity which is affected by various factors such as government policies, political situations, public events, internal company politics and much more. However there is no way of knowing exactly which factor will affect stock prices and how much the price will be affected. Financial trend forecasting is a major component in corporate finance because predictions of future prices, indices, volumes and several other values are often incorporated into the economic decision-making process for a particular company. For the average investor financial trend forecasting would mean a greater profit (or smaller loss). To recognize specific trends for forecasting capabilities, it is important to develop a method for eliminating speculation and to investigate new algorithms for detecting patterns. Although there are many different approaches available, in this thesis a comparison between an unsupervised classification technique, namely K-means clustering, and supervised learning algorithms, namely support vector machines and radial basis functions, will be performed. The three pattern recognition systems will be tested against real-world data concerning the U.S. 30-Year Treasury bond yield. Determining the yield trend is approached as a technical analysis problem for this particular study: ignoring underlying factors and focusing on finding patterns directly from historical data. The results from each of the three networks are compared and analyzed. The performance measures analyzed include accuracy percentages, return on investment ratios, as well as capital gains/losses. From this analysis, a general network model can be decided upon to forecast the U.S. 30-Year Treasury bond yield. Show less

In this manuscript, a computer simulation model for the study of the large-scale effects on narrowband transmission systems is proposed to validate the existing semi-empirical models. The development of the computer simulation path-loss model is based on the ray tracing technique. It is emphasized that multipath signals are considered in this model. This study only concentrates on the first-order scattering effects, namely each multipath signal is a two-hop signal that involves a single... Show moreIn this manuscript, a computer simulation model for the study of the large-scale effects on narrowband transmission systems is proposed to validate the existing semi-empirical models. The development of the computer simulation path-loss model is based on the ray tracing technique. It is emphasized that multipath signals are considered in this model. This study only concentrates on the first-order scattering effects, namely each multipath signal is a two-hop signal that involves a single scattering object. The first hop is directed toward the scatterer from the transmitter (TX); and the second hop goes from the scatterer to the receiver (RX). Each hop signal is described using a two-ray model due to direct-path propagation and ground-reflected path propagation. When the number of scattering objects is large, the simulation results are consistent with the semi-empirical models that are based on measurements, including the Hata model, the Lee model, and the model reported in [3]. Typically, the path-loss increases linearly with log distance. However, when the number of scattering objects is small, the linear model for path loss is not universally valid. In particular, when the path loss and log distance are weakly correlated in a linear manner, the linear model may lead to physically unrealizable results. This observation has not been made by the various groups that studied channel modeling based on measurements. In addition, the proposed model enjoys the flexibility in studying the effects of scattering object density in the channel, the radar cross section of the scattering objects, the ground reflection coefficients, and the distance between the TX and the RX. Furthermore, coherent multipath signals can cause the path-loss exponent to fall below 2, which corresponds to free-space propagation. Show less

Bridges in Florida are exposed to high amounts of humidity due to the state's geography. This excess moisture results in a high incidence of corrosion on the bridge's steel support cables. Also, the inclusion of ineffective waterproofing has resulted in additional corrosion. As this corrosion increases, the steel cables, responsible for maintaining bridge integrity, deteriorate and eventually break. If enough of these cables break, the bridge will experience a catastrophic failure resulting... Show moreBridges in Florida are exposed to high amounts of humidity due to the state's geography. This excess moisture results in a high incidence of corrosion on the bridge's steel support cables. Also, the inclusion of ineffective waterproofing has resulted in additional corrosion. As this corrosion increases, the steel cables, responsible for maintaining bridge integrity, deteriorate and eventually break. If enough of these cables break, the bridge will experience a catastrophic failure resulting in collapse. Repairing and replacing these cables is very expensive and only increases with further damage. As each of the cables is steel, they have strong conductive properties. By inducing a current along each group of cables and measuring its dissipation over distance, a picture of structural integrity can be determined. The purpose of this thesis is to prove the effectiveness of using electromagnetic techniques to determine cable integrity. By comparing known conductive values (determined in a lab setting) to actual bridge values, the tester will be able to determine the location and severity of any damage, if present. Show less

Date Issued

2014

Identifier

FSU_migr_etd-8877

Format

Thesis

Title

Design and Analysis of Segmented Sensor for Road Traffic Classification.

Individual vehicle information, specially, vehicle classification data play a key role in road traffic measurement. In inductive loop and piezoelectric sensor systems, traffic data such as number of axles and the distance between axles are used for vehicle classification. However, classification errors occur in distinguishing class 3 (long bed pickup truck) and class 5 (small truck) vehicles that are moving at highway speeds. In order to overcome these classification errors and improve the... Show moreIndividual vehicle information, specially, vehicle classification data play a key role in road traffic measurement. In inductive loop and piezoelectric sensor systems, traffic data such as number of axles and the distance between axles are used for vehicle classification. However, classification errors occur in distinguishing class 3 (long bed pickup truck) and class 5 (small truck) vehicles that are moving at highway speeds. In order to overcome these classification errors and improve the durability, a new extruded polymer segmented sensor approach is developed. Segmented sensor has an additional ability to provide an estimate of the tire width to discriminate between different tire types and classify vehicles accurately. The extruded polymer conductors used in the existing prototype segmented sensor have a very high resistance that was found to limit the frequency response of the sensor. Segmented sensor with limited frequency response could not always properly identify the closed segments for vehicle moving at highway speeds. Several analysis and simulations were conducted to improve the performance of the extruded segmented sensor. In this thesis, previous efforts conducted in designing interface electronics of segmented sensor and continued efforts on designing an accurate simulation model for extruded polymer segmented sensor with its detection electronics are discussed. Contribution to the current research work on extruded segmented sensor include validating Dr. Bourner's 3x3 segmented sensor model, applying the 3x3 segmented sensor approach to existing extruded polymer segmented sensor and comparing the results with measured responses of existing 16-segmented extruded polymer sensor to develop an accurate simulation model. The cross-sectional dimensions are then increased to get an improved frequency response. Further 16-segmented extruded model is extended to a 49-segmented simulation model based on the foot print results provided by Dr. Ren Moses. Also the final model with increased cross-section is simulated to attain the required bandwidth needed to design a new prototype of extruded segmented sensor that can classify vehicles moving at highway speeds. Show less

Date Issued

2013

Identifier

FSU_migr_etd-7395

Format

Thesis

Title

Design and Modeling of Very High-Efficiency Multijunction Solar Cells.

The main challenge in the solar cell industry is making the solar cells more cost effective. Mono and poly-crystalline Si, CdTe, CIGS, Quantum dot, Organic and Dye-sensitized solar cell technologies do not produce high efficiencies. A low bandgap semiconductor generates larger current due to photon absorption over broader spectral region but do not produce high open circuit voltage because it is limited by the dark current of the low bandgap material. This limits them within the Shockley... Show moreThe main challenge in the solar cell industry is making the solar cells more cost effective. Mono and poly-crystalline Si, CdTe, CIGS, Quantum dot, Organic and Dye-sensitized solar cell technologies do not produce high efficiencies. A low bandgap semiconductor generates larger current due to photon absorption over broader spectral region but do not produce high open circuit voltage because it is limited by the dark current of the low bandgap material. This limits them within the Shockley efficiency limit of 30%. The relevant solutions are to increase the efficiency of solar cells, for example by effective spectral splitting by different bandgap semiconductor subcell layers, implementation of III-V direct bandgap optically sensitive and high carrier mobility semiconductors, form better matching (lattice, optical and electrical) between subcell layers, usage of concentrator Fresnel lenses and most importantly reduce the fabrication cost of the epitaxial layers. In this work we introduced two novel quadruple junction solar cell designs, each having four semiconductor subcell layers. We have simulated the quantum efficiency vs. wavelength, current density vs. voltage, power density vs. voltage and compared the photon absorption of our two novel designs with state of art single junction and multijunction solar cells. We showed that antimony based subcell layers help in higher photon absorption in the infrared (IR) region. Photonic modeling is implemented by the transfer-matrix method of wave propagation through multilayer structures. The first quadruple junction solar cell design comprises of AlGaInP (2.3eV) / InGaAs (1.1eV) / GaSb (0.7eV) / InGaSb (0.5eV) and the second design comprises of AlGaInP (2.3eV) / InGaP (1.93eV) / InGaAs (1.1eV) / InGaSb (0.5eV) III-V direct-bandgap semiconductor materials. The quadruple-junction subcell layers capture photons of ultraviolet (UV), visible, and near- and far infrared (IR) regions of the electromagnetic spectrum. The combination of our subcell layers yield favorable photon absorption results in comparison to the state of art solar cells. Show less

Date Issued

2013

Identifier

FSU_migr_etd-7296

Format

Thesis

Title

A Design Methodology for the Implementation of Fuzzy Logic Traffic Controller Using Field Programmable Gate Array.

In this thesis, an approach is proposed for the design and implementation of fuzzy traffic controllers using Field Programmable Gate Arrays (FPGAs).The focus of this study is to develop an effective traffic signaling strategy to be implemented at a typical intersection with four approaches. Adaptive traffic control using fuzzy principles has been demonstrated and reported by the authors in the literature. Here a high-level design approach is suggested, which involves VHDL-based logic... Show moreIn this thesis, an approach is proposed for the design and implementation of fuzzy traffic controllers using Field Programmable Gate Arrays (FPGAs).The focus of this study is to develop an effective traffic signaling strategy to be implemented at a typical intersection with four approaches. Adaptive traffic control using fuzzy principles has been demonstrated and reported by the authors in the literature. Here a high-level design approach is suggested, which involves VHDL-based logic synthesis and the use of state diagrams with a VHDL backend for graphical design description. The operations of the fuzzifier and the defuzzifier of the fuzzy controller are described in VHDL. The fuzzy rule base for the controller is described using the state diagrams. Specifically, the fuzzy inference based on the fuzzy rules is implemented using MATLAB code. The output of the MATLAB program is stored in a ROM for use in the VHDL code. Once VHDL code is obtained then the hardware is implemented using the UP1 Education board. After the design was tested by using UP1 board the next step was to design a printed circuit board for this system. This was done by using Protel Design Explorer where the input to the circuit board comes from traffic sensors in the field and the output of the circuit board is given to the traffic controller. Show less

Date Issued

2004

Identifier

FSU_migr_etd-0028

Format

Thesis

Title

Design of a Compact Microstrip Patch Antenna for Use in Wireless/Cellular Devices.

The cellular industry came into existence 25 years ago and as of today, there are approximately 150 million subscribers worldwide. The cellular industry generates $30 billion in annual revenues and is one of the fastest growing industries. The cellular handsets being used in the 1980s were bulky and heavy. Advancements in VLSI technology have enabled size reduction for the various microprocessors and signal processing chips being used in cellular phones. Another method for reducing handset... Show moreThe cellular industry came into existence 25 years ago and as of today, there are approximately 150 million subscribers worldwide. The cellular industry generates $30 billion in annual revenues and is one of the fastest growing industries. The cellular handsets being used in the 1980s were bulky and heavy. Advancements in VLSI technology have enabled size reduction for the various microprocessors and signal processing chips being used in cellular phones. Another method for reducing handset size is by using more compact antennas. The aim of this thesis is to design such a compact antenna for use in wireless/cellular devices. A Microstrip Patch Antenna consists of a dielectric substrate on one side of a patch, with a ground plane on the other side. Due to its advantages such as low weight and volume, low profile planar configuration, low fabrication costs and capability to integrate with microwave integrated circuits (MICs), the microstrip patch antenna is very well suited for applications such as cellular phones, pagers, missile systems, and satellite communications systems. A compact microstrip patch antenna is designed for use in a cellular phone at 1.9 GHz. The results obtained provide a workable antenna design for incorporation in a cellular phone. Show less

Date Issued

2004

Identifier

FSU_migr_etd-2790

Format

Thesis

Title

Design of Custom Instruction Set for FFT Using FPGA-Based Nios Processors.

Nios Embedded processors provide a powerful, robust platform for developing and implementing complex algorithms. The unique custom instruction feature of Nios processors could be used to enhance the performance of these algorithms dramatically, while reducing the size and complexity of software. This feature involves implementing a part or entire algorithm in hardware and making it accessible to software through specially generated software macros known as custom instructions. Currently, fast... Show moreNios Embedded processors provide a powerful, robust platform for developing and implementing complex algorithms. The unique custom instruction feature of Nios processors could be used to enhance the performance of these algorithms dramatically, while reducing the size and complexity of software. This feature involves implementing a part or entire algorithm in hardware and making it accessible to software through specially generated software macros known as custom instructions. Currently, fast Fourier transform (FFT) algorithms play an important role in many of the digital signal processing applications that are highly time critical. Hence there is a need to increase the performance of these algorithms. In the thesis, the decimation-in-frequency radix-2 FFT is implemented using custom instruction for the butterfly processor present in the algorithm. The performance enhancement of the custom implementation of this algorithm is then measured against software-only implementation. Show less

Large-scale storage arrays are always in high demand by universities, government agencies, web search engines, and research laboratories. This unvarying need for more data storage has begun to push storage array magnitudes into an unknown stratum. As storage systems continue to outgrow the terabyte class and move into the petabyte range, these colossal arrays begin to show design limitations. This thesis focuses primarily on disk drives as the building blocks of reliable large-scale storage... Show moreLarge-scale storage arrays are always in high demand by universities, government agencies, web search engines, and research laboratories. This unvarying need for more data storage has begun to push storage array magnitudes into an unknown stratum. As storage systems continue to outgrow the terabyte class and move into the petabyte range, these colossal arrays begin to show design limitations. This thesis focuses primarily on disk drives as the building blocks of reliable large-scale storage arrays. As a feasibility baseline, the overall reliability of large-scale storage arrays should be greater than that of a single disk. However, petabyte- and exabyte-sized systems, requiring thousands to millions of disk drives, present a serious challenge in terms of reliability. Therefore, multi-level redundancy schemes must be used in order to slow these dwindling reliabilities. This work, based upon the previous research of redundant arrays of independent disks (RAID) by Patterson et al., introduces the reliability analysis of dual- and tri-level Grouped RAID (GRAID) configurations. As storage arrays rapidly increase in size, the use of multi-level redundancy is essential. Design recommendations for various large-scale storage arrays, ranging from 100 Tebibytes (TiB) to 100 Exbibytes (EiB), can be generated using the custom reliability calculator tool written in MATLAB. The analysis of these design recommendations shows that dual-level GRAID configurations are only recommended for array magnitudes up to 5 PiB. Beyond this threshold, tri-level GRAID demonstrates feasibility for storage magnitudes up to 100 EiB and beyond. Show less

Date Issued

2007

Identifier

FSU_migr_etd-2579

Format

Thesis

Title

Determination of Carbon Nanotube Thin Film Thickness and Optical Parameters by a New Modified Prism Waveguide Coupler System.

Since their discovery by Iijima in 1991 carbon nanotubes have been used in many novel applications of nanotechnology. Carbon nanotubes thin films in particular can be used to create, among others, anti-reflection coatings or stretch sensors. However, for these applications to be successful the thickness of the film as well as its refractive index must be known. In this thesis a new system capable to measure the thickness and index of such films is proposed. Based on thin film optics, during... Show moreSince their discovery by Iijima in 1991 carbon nanotubes have been used in many novel applications of nanotechnology. Carbon nanotubes thin films in particular can be used to create, among others, anti-reflection coatings or stretch sensors. However, for these applications to be successful the thickness of the film as well as its refractive index must be known. In this thesis a new system capable to measure the thickness and index of such films is proposed. Based on thin film optics, during 1969 Tien, Ulirch, and Martin first proposed a prism coupler method that could be used determine the characteristics of a transparent film by guiding light inside it. Based on their work Metricon corporation developed the first commercialized prism coupler instrument. Later, Liu developed a method called IRIA (Internal Reflected Intensity Analysis) that can be used to determine the characteristics of highly absorbing samples. Here based on the IRIA method a new modified prism coupler system is proposed. After the validity of the system's output is verified by comparing the acquired results with the results acquired from other methods, the new system is used to measure the thickness and the refractive index of single walled carbon nanotube thin films deposited on Polydimethylsiloxane substrates. Show less

Date Issued

2013

Identifier

FSU_migr_etd-7285

Format

Thesis

Title

Development and Implementation of a 25 kVA Phasor-Based Virtual Machine.

A motor drive system should be reliable, efficient, and robust under numerous applications, loads, and control schemes. To ensure such characteristics and fully test the range of operation for a motor drive, manufacturers and developers traditionally must have a wide assortment of test bed equipment to recreate various machine load combinations. During motor drive development stages, expensive hardware is exposed to faulting and instability risks prior to completely debugging the product. The... Show moreA motor drive system should be reliable, efficient, and robust under numerous applications, loads, and control schemes. To ensure such characteristics and fully test the range of operation for a motor drive, manufacturers and developers traditionally must have a wide assortment of test bed equipment to recreate various machine load combinations. During motor drive development stages, expensive hardware is exposed to faulting and instability risks prior to completely debugging the product. The associated risks and expenditures increase with the power level. Therefore, this thesis provides a motor drive testing method, deemed the "virtual machine," (VM) that removes a great deal of the risk and cost associated with motor drive development and validation. The technique used to accomplish the VM exploits the Power Hardware in the Loop (PHIL) concept to replace equipment; particularly a voltage amplifier is used to recreate the terminal characteristics of various machine loading scenarios that a motor drive is conventionally tested against. A unique transformer coupling network is proposed between the amplifier and motor drive to provide decoupling and properly step voltages. By implementing the VM concept on such a transformer coupled PHIL test bed, potential pitfalls and non-linearities due to the transformer can be assessed; thus, providing the field with a new PHIL filter structure and de risking the design prior any future increments in power level. When validating, the VM shows matching, consistent results compared against both simulations and a physical induction machine (IM) energized via the same motor drive. Note that multiple counter torque loads were provided via a DC machine. Although the proposed amplifier control method is based on a steady state phasor system, it also proves adequate for recreating the transient terminal characteristics of an IM across the line start. The conclusion proves the VM concept a viable solution for removing cost and risk in drive development as well as verifies the PHIL transformer coupling network. The concept of controlling active and reactive power flow between parallel connected LCL coupled converters is established then applied as a PHIL technique; thus, opening the field to use this approach for evaluating more complex, simulated systems. The limitations of the proposed method are discussed as well as future work areas to address such constrictions and improve the fidelity of the VM. Finally, after polishing the limitations, a future direction of increasing the VM power level is established and some derivatives of the PHIL load emulation concept given. Show less

Date Issued

2010

Identifier

FSU_migr_etd-4438

Format

Thesis

Title

Development of a Virtual Grid Interface for Phev Integration Analysis.

Recent increased popularity in plug-in hybrid electric vehicles (PHEVs) has been influenced by their ability to relieve the economic dependence on oil, meanwhile reducing the carbon footprint through the decreased level of harmful emissions. However, PHEV popularity has not come without a cost. PHEVs main source of power are their internal energy storage systems which require energy from the grid through a form of charging station. This need to charge creates a power consumption dilemma on... Show moreRecent increased popularity in plug-in hybrid electric vehicles (PHEVs) has been influenced by their ability to relieve the economic dependence on oil, meanwhile reducing the carbon footprint through the decreased level of harmful emissions. However, PHEV popularity has not come without a cost. PHEVs main source of power are their internal energy storage systems which require energy from the grid through a form of charging station. This need to charge creates a power consumption dilemma on the ever-strained power system from population growth and the consumer use of power for current everyday technologies. To study the effects that the charging PHEVs will have on the system, two studies were performed within the scope of this thesis: a system study involving the IEEE 14-Bus and a subsystem study that will incorporate the development of a virtual grid interface. The system study populated the IEEE 14-Bus system with constant power loads to observe the additional power requirements on the supply generators when integrating PHEVs into the system in an incremental fashion. Also, charging method impacts were conducted by creating uncontrolled and controlled charging profile loadings with the PHEVs. The second study developed a laboratory environment with the intent of emulating a grid-connected charging PHEV, also known as a virtual grid interface. This grid interface will be tested to show proof of concept and then applied to a set of hardware to demonstrate the negative effects of uncontrolled front ends within charging station. Subsequently, the mitigation of the aforementioned negative effects will be illustrated through the employment of an active front end within the charging station. The conclusion provides an understanding for affects from charging PHEVs and the importance in developing controls within the charging stations in order to mitigate undesirable charging impacts. Additionally, the vast range of applications for which the developed virtual grid interface can be used for is discussed, along with some of the limitations and future works of the system. Show less

In this thesis, a mixture of acetonitrile (AN) and γ-butyrolactone (γBL) are used as the solvent in combination with LiClO4 or LiBF4 as the salt of the electrolyte studied for Li-ion capacitors. The electrolyte with various ratios of AN and γBL with different salts are investigated, and visual observation shows that metallic lithium is stable in LiClO4 or LiBF4 in 1:1 (wt.) AN/γBL electrolyte. The ionic conductivity of the electrolyte as a function of LiClO4 salt is optimized, and it is shown... Show moreIn this thesis, a mixture of acetonitrile (AN) and γ-butyrolactone (γBL) are used as the solvent in combination with LiClO4 or LiBF4 as the salt of the electrolyte studied for Li-ion capacitors. The electrolyte with various ratios of AN and γBL with different salts are investigated, and visual observation shows that metallic lithium is stable in LiClO4 or LiBF4 in 1:1 (wt.) AN/γBL electrolyte. The ionic conductivity of the electrolyte as a function of LiClO4 salt is optimized, and it is shown that 1M LiClO4 in 1:1 (wt.) AN/γBL electrolyte has the highest conductivity which is much higher than a commercial electrolyte (1M LiPF6 in 1:1:1 (wt.) ethylene carbonate (EC)/Dimethyl carbonate (DMC)/diethyl carbonate (DEC)) used in Li-ion batteries, over the whole temperature range from -30℃ to 65℃. The electrochemical stability windows of three electrolytes, 1M LiPF6 1:1:1 (wt.) EC/DMC/DEC, 1.1M LiClO4 in 1:1 (wt.) AN/γBL and 1M LiBF4 in 1:1 (wt.) AN/γBL, on three kinds of electrodes (GC, AC and HC) are different from each other, and the results are compared and discussed. The discharge and charge cycling results show that Li/AC cells with both 1.1M LiClO4 in 1:1 AN/γBL and 1M LiBF4 in 1:1 AN/γBL electrolytes have fast capacity decay due to the increased impedance. The capacity of the latter was higher initially but decayed more rapidly which can be probably attributed to the product covered on the surface of the AC electrode. Show less

Increased penetration of solar PV has risen the level of concern among utilities about its potential impact on the system operation and reliability. Reverse powerflow, rise in voltage, unnecessary operations of traditional voltage regulation devices, harmonics, PV islanding, sympathy trips during feeder faults, flicker, etc. are some of the concerns mentioned in 1547.7 which deals with impact of distributed generation (like solar PV) on distribution feeders. One of the main concerns for... Show moreIncreased penetration of solar PV has risen the level of concern among utilities about its potential impact on the system operation and reliability. Reverse powerflow, rise in voltage, unnecessary operations of traditional voltage regulation devices, harmonics, PV islanding, sympathy trips during feeder faults, flicker, etc. are some of the concerns mentioned in 1547.7 which deals with impact of distributed generation (like solar PV) on distribution feeders. One of the main concerns for utility is voltage on a feeder and its regulation. The studies conducted in this thesis go beyond the current IEEE 1547 practices, `The Standard for Interconnecting Distributed Resources with Electric Power Systems', which gives recommended practices for DG interconnection. Current standards limit PV Inverters to inject real power only and not participate in voltage regulation. But with several studies showing the benefits of using the readily available capability of inverter to inject reactive power and regulate voltage is being explored which will pave way for the new IEEE 1547 amended guidelines which would allow PV inverters to regulate voltage and supply reactive power. For this study, the PV inverters were allowed to supply reactive power and regulate voltage. In doing so, an investigation of interactions between PV inverters and traditional voltage regulation equipments like tap changing transformer (OLTC), switched capacitor bank (SCB), and step voltage regulator (SVR) were made. The study was conducted on two distinct Florida utility distribution feeders that have high penetration of PV and voltage regulation devices. One of the feeder has single large PV plant (15 MW) while the other feeder has large multiple PV plants (2.6 MW) which amounts to penetration levels of 100% and 35% respectively. Distribution feeder were modeled on an EMTP tool (RTDS) and validated against data provided by the utility. The study focuses on how different PV penetration levels and load levels on the feeder impact operation of voltage regulation devices. In doing so, the study aims at using different operating constraints for OLTC, SCB and SVR. Some candidate methods of operating constraints for OLTC, SCB and SVR are voltage, time, temperature, real power flow, reactive power flow, and combination of any methods mentioned above. As mentioned before, in going beyond the current scope of IEEE 1547, PV inverters were allowed to supply reactive power and different candidate methods currently available on inverter like constant Q, power factor, voltage based and advanced control strategies like German LV std. curve, Volt-VAR curve, Volt-pf curve were used to investigate and mitigate any possible interactions between devices. Possible best suited methods and practices were laid out incase there is an unnecessary interaction between PV inverters and OLTC, SCB and SVR for each feeder. The major observations from this study are: 1. Allowing PV inverters to regulate voltage may not necessarily increase or decrease interactions with voltage regulation devices. 2. Some of the key factors which influence interactions between voltage regulation devices and PV are feeder circuit layout (e.g. overhead line vs. cable,), voltage level, length of feeder, etc), nature of loads, location and size of loads, and location of PV. 3. Based on the cases studied within this work no common trait for defining high penetration PV circuit studies could found. 4. No correlation between PV penetration level, measured by the amount of installed PV capacity vs. feeder loading, and the severity of impact of PV on the circuit operational characteristics could be found in this study. Concluding from this work is recommended to establish a new set of metrics which truly define the impact severity of PV on distribution feeders, since the current metric of PV penetration level is clearly inadequate. Show less

Wireless Communication has been a rapidly growing industry over the past decade. The mobile and portable device market has boomed with the advent of new data, multi-media and voice technologies. The technical advances in mobile and personalized computer fields have accelerated wireless communication into a crucial segment of the communication industry. Introduction of smart phones and hand held devices with internet browsing, email, and multi-media services, has made it essential to add... Show moreWireless Communication has been a rapidly growing industry over the past decade. The mobile and portable device market has boomed with the advent of new data, multi-media and voice technologies. The technical advances in mobile and personalized computer fields have accelerated wireless communication into a crucial segment of the communication industry. Introduction of smart phones and hand held devices with internet browsing, email, and multi-media services, has made it essential to add features like security, reliability etc over the wireless network. Wireless sensor networks which are a subset of the wireless ad hoc networks have been deployed in various military and defense applications. The popularity of 802.11 technologies have led to large scale manufacturing of 802.11 chipsets and reduced the cost drastically. Thus enabling deployment of large scale wifi networks resembling sensor environment. As wireless communication uses air interface it is challenging to support such advanced QoS (Quality Of Service), features due to external interference. Some of the typical interference encountered is from other electronic devices like microwaves, environmental interference like rain, and from physical structures like buildings. Also it is a known fact that battery technology hasn't kept pace with the electronics industry. Consequently to add portability to these wireless devices it has become essential to cut down on energy sources embedded within these devices. Hence wireless equipment designers have to combat interference with minimal power expenditure. To best utilize the limited resources of these wireless devices and guarantee QoS it is essential to design specialized algorithms spanning across all layers of the network. These algorithms should not only take into account the network parameters but also dynamically adapt to the changes in the network configurations, traffic etc. The complete set of such techniques constitutes what can be described as Dynamic Resource Management In Wireless Networks. The proposed research was aimed to design techniques such as dynamic channel allocation, energy efficient clustering and reliable power aware routing. Clustering is one of the energy efficient architecture in wireless ad hoc networks and more specifically used in sensor network like environment. Clustering is achieved by grouping devices together based on location, traffic generation etc. Clustering not only limits energy spent by devices in communication, but also aids in better utilization of channel by avoiding collisions. Clustering makes sure that devices communicate with their respective cluster head with minimal required power thereby causing very less interference to the devices in the neighboring cluster. It also makes it possible to combine and compress the information at the CH (Cluster Head) before relaying it to the central collection or base station Show less

Wavelets are mathematical functions that cut up data into different frequency components, and then study each component with a resolution matched to its scale. Wavelets are an extremely useful tool for coding images and other real signals. Because the wavelet transform is local in both time (space) and frequency, it localizes information very well compared to other transforms. Wavelets code transient phenomena, such as edges, efficiently, localizing them typically to just a few coefficients.... Show moreWavelets are mathematical functions that cut up data into different frequency components, and then study each component with a resolution matched to its scale. Wavelets are an extremely useful tool for coding images and other real signals. Because the wavelet transform is local in both time (space) and frequency, it localizes information very well compared to other transforms. Wavelets code transient phenomena, such as edges, efficiently, localizing them typically to just a few coefficients. This thesis deals with the different types of edge detection techniques, mainly concentrating on the two major categories Gradient and Laplacian. The gradient method detects the edges by looking for the maximum and minimum in the first derivative of the image. The Laplacian method searches for zerocrossings in the second derivative of the image to find edges. Given the wavelet transforms values wavelet analysis can be done in the wavelet domain by comparison of wavelet coefficients that account for the edges. The detection of the maxima or inflection points is generally a key factor for analyzing the characteristics of the non-stationary signals. The wavelet transformation has been proved to be a very promising technique for the multiscale edge detection applied both to 1-D and 2-D signals. The dyadic wavelet transforms at two adjacent scales are multiplied as a product function to magnify the edge structures and suppress the noise. Unlike many multiscale techniques that first form the edge maps at several scales and then synthesize them together, we determined the edges as the local maxima directly in the scale product after an efficient thresholding. It is shown that the scale multiplication achieves better results than either of the two scales, especially on the localization performance. The thesis deals with the comparison of edge detection of images using traditional edge detection operators (Prewitt, Sobel, Frei-chen and Laplacian of Gaussian) and Discrete Wavelet Transformation (DWT) using Haar, Daubechies, Coifman and Biorthogonal wavelets. It also deals with the edge detection of noisy images and the optimization of the wavelets for edge detection. Show less

This dissertation addresses the development of efficient digital filter implementation techniques. Measures for area, latency, and throughput are used to quantify the benefits of the proposed implementation schemes, as well as consideration of the digital signal processing algorithm performance. Multiple-constant multiplication (MCM) is a popular approach for implemented fixed coefficient finite impulse response (FIR) filters. We propose two methods for truncating addition results in an MCM... Show moreThis dissertation addresses the development of efficient digital filter implementation techniques. Measures for area, latency, and throughput are used to quantify the benefits of the proposed implementation schemes, as well as consideration of the digital signal processing algorithm performance. Multiple-constant multiplication (MCM) is a popular approach for implemented fixed coefficient finite impulse response (FIR) filters. We propose two methods for truncating addition results in an MCM implementation that reduce the area required while decreasing latency. The effects of filter order and coefficient quantization are explored by the proposed search technique that reduces the computations required by an MCM implementation. Two new adaptive filter implementation techniques based on distributed arithmetic (DA) are proposed that provide reduced area and speed without loss of filter performance. Adaptive filter implementations can also be based on real-time conversion of the adapted coefficients into a canonical-signed-digit (CSD) representation. We propose a new conversion circuit that reduces both latency and area. Fine-grained parallelism and relaxed look-ahead techniques are applied to develop a pipelined Gauss-Seidel fast affine projection (GSFAP) adaptive filter implementation that allow degradation to the adaptive filter performance and increases area to achieve significantly faster performance. These proposed techniques for fixed coefficient and adaptive filters can be used for applications in which low area and high speed implementations are required. Show less

Recently the Wavelet Transform has gained a lot of popularity in the field of signal processing. This is due to its capability of providing both time and frequency information simultaneously, hence giving a time-frequency representation of the signal. The traditional Fourier Transform can only provide spectral information about a signal. Moreover, the Fourier method only works for stationary signals. In many real world applications, the signals are non-stationary. One solution for processing... Show moreRecently the Wavelet Transform has gained a lot of popularity in the field of signal processing. This is due to its capability of providing both time and frequency information simultaneously, hence giving a time-frequency representation of the signal. The traditional Fourier Transform can only provide spectral information about a signal. Moreover, the Fourier method only works for stationary signals. In many real world applications, the signals are non-stationary. One solution for processing non-stationary signals is the Wavelet Transform. Currently, there is tremendous focus on the application of Wavelet Transforms for real-time signal processing. This leads to the demand for efficient architectures for the implementation of Wavelet Transforms. Due to the demand for portable devices and real-time applications, the design has to be realized with very low power consumption and a high throughput. In this thesis, different architectures for the Discrete Wavelet Transform filter banks are presented. The architectures are implemented using Field Programmable Gate Array devices. Design criteria such as area, throughput and power consumption are examined for each of the architectures so that an optimum architecture can be chosen based on the application requirements. In our case study, a Daubechies 4-tap orthogonal filter bank and a Daubechies 9/7-tap biorthogonal filter bank are implemented and their results are discussed. Finally, a scalable architecture for the computation of a three-level Discrete Wavelet Transform along with its implementation using the Daubechies length-4 filter banks is presented. Show less

Field programmable gate arrays (FPGAs) are becoming increasingly prevalent in embedded digital signal processing applications. Faster clock speeds (now at 500 MHz), greater logic density, and dedicated embedded DSP hardware blocks are facilitating signal processing performance up to 1000 times faster than modern microprocessors. Improved computer aided design tools are allowing logic designers to implement ever more complex algorithm in field programmable logic. This thesis will present the... Show moreField programmable gate arrays (FPGAs) are becoming increasingly prevalent in embedded digital signal processing applications. Faster clock speeds (now at 500 MHz), greater logic density, and dedicated embedded DSP hardware blocks are facilitating signal processing performance up to 1000 times faster than modern microprocessors. Improved computer aided design tools are allowing logic designers to implement ever more complex algorithm in field programmable logic. This thesis will present the design and implementation details of a pattern classification algorithm specifically tuned for implementation in an FPGA's reconfigurable fabric. The reconfigurable solution presented compares favorably with a desktop PC based implementation when considering classification throughput. Additionally, the FPGA based system has power and space requirements roughly two orders of magnitude smaller than the PC, thus making it a more suitable candidate for embedded applications. Show less

A wireless sensor network (WSN) consists of a large number of low-cost sensors that can communicate to each other for specific applications. Sensor nodes are spatially distributed in a large region and operated in an autonomous manner. Each sensor node in the network is battery-limited and irreplaceable for most applications. Compared to the existing ad-hoc networks, significant problems have been raised. How to efficiently consume the energy to obtain a long lifetime of the network? How to... Show moreA wireless sensor network (WSN) consists of a large number of low-cost sensors that can communicate to each other for specific applications. Sensor nodes are spatially distributed in a large region and operated in an autonomous manner. Each sensor node in the network is battery-limited and irreplaceable for most applications. Compared to the existing ad-hoc networks, significant problems have been raised. How to efficiently consume the energy to obtain a long lifetime of the network? How to design routing algorithms to adaptively accommodate the change in energy? How to reconsider the energy-efficiency issue if the renewable energy devices are involved? How to mathematically model these problems and validate solutions by simulations and experiments? We investigate these questions and present our models, designs, algorithms, and results in the dissertation. Research on WSNs is driven by specific applications but the applications of WSN have been widely divergent in recent years. Environmental monitoring and surveillance is a major application, in which the WSN is implemented to monitor a large geographic area that is usually unexplored or potentially dangerous area, such as forests, rivers, and desert. It is especially challenging when the infrastructure of the environment is unknown. The sensors for this application are irreplaceable and thus the battery life becomes crucially important. Military applications are designed to support communications among soldiers, military vehicles, and headquarters. For example, in a battlefield, the coordination among a groups of soldiers has to be well-established in any complicated situation. An interesting paradigm is animal monitoring, in which small sensors are placed on animals to surveil their habitat. The sensors carried by animals form a mobile ad hoc network to collect and transmit data. The difficulties of this application are that the sensors must be lightweight enough for animals while the topology of the network is always changing. Also, there are other emerging applications like body health monitoring, disaster recovery, and underwater robot-assisted exploration. In this work, we have two major related research topics. One is the energy-efficient design and optimization of the application-specific routing protocols to maximize the network lifetime of a WSN. Another is the optimization and design of the routing protocol for energy harvesting wireless sensor network (EHWSN) by predicting the condition of energy harvesting in the near future. For the first topic, the key issue is how to conserve energy to maintain the network connectivity as long as possible, or maximize the lifetime of the network. One common solution is to design a routing algorithm that can cope with the changes of network conditions and dynamically adjust the routing strategy or switch the operation modes to save energy. Many routing metrics have to be considered including transmission distance, residual energy, link capacity, etc. Energy-efficient routing protocols have been well investigated with the goal of maximizing the network lifetime, which is usually defined as the time when the first node dies. Once a node becomes unavailable due to energy depletion, its data transmissions in the network are assumed to fail. In our work, we consider the network remains alive as long as the energy is enough to maintain the flows of the application traffic, which is more reasonable since the network can still function even without those "dead" nodes. Instead of universally balancing the energy consumption over the entire network, we aim at locally optimizing the energy-efficiency of the target nodes on the application flows. Essentially, it’s an energy trade-off between the target nodes and other irrelevant nodes, in which the former will expend more energy than the latter on the application flows for energy-efficiency. Therefore, the routing algorithm can be designed to save more energy on routes of the specific traffic. We present a novel application-specific and energy-efficient routing algorithm to maximize the lifetime of the application flows in WSNs. Firstly, we formulate the routing problem as a linear programming problem, which can be converted to a max-min fairness problem. Secondly, the lifetime of a flow is evaluated in terms of the link metrics including residual energy, transmission rate, and link distance. Thirdly, a heuristic routing algorithm is proposed to compute the best route that minimizes the cost of application flows. Simulation results have shown that our routing algorithm prolong the lifetime of flows around 10%. For the second topic, compared to a conventional WSN, which is strictly limited by its battery supply of the sensor nodes, EHWSN is an environmentally powered network that brings new techniques and challenges to the energy-efficiency topic. By harvesting the ambient or renewable energy feasible to WSN, a tremendous breakthrough can be made to improve the energy-efficiency and the network lifetime. Environment usually has a large variety of the energy sources, such as solar, wind, mechanical, thermal, and biochemical sources. Some major issues have been raised in order to take advantage of energy harvesting. For instance, how to schedule and allocate the energy consumption by predicting the energy availability? How to jointly consider the energy-efficiency and network lifetime? How to design a prediction model for energy harvesting in order to achieve a better performance? We find a critical issue in current routing algorithms for EHWSN, in which the calculated routes are frequently alternating because of the uncertainty of the energy availability in the near future. Without knowing the future harvesting condition, the current algorithms calculate the most energy-efficient routes based on the past and current condition. The uncertainty may lead to energy waste and extra network overheads. In our work, we propose to predict the energy harvesting condition in the near future and estimate whether the current optimal routes can be maintained by the harvested energy in a certain time threshold. If yes, we temporarily restrict the data transmission and receiving to reduce the energy cost by using parameters, which are determined by the availability and intensity of the future harvesting. Comprehensive factors are considered to predict the energy condition in near future and help make routing decisions including residual energy, harvest energy, and energy consumption. We first give an example to illustrate the motivation of our energy prediction-based routing problem. Second, we formulate the problem as a linear optimization problem and convex optimization problem with analytical proof depending on prediction models. Third, we propose a heuristic routing algorithm to maximize the volume of collected data from the network. Fourth, the routing algorithm is implemented and verified by Matlab and OMNET++ simulation. The results indicate that the proposed algorithm can largely improve the energy-efficiency and reduce the network overheads. In summary, we propose to solve the energy-efficiency issues in both application-specific WSN and EHWSN. For application-specific WSN, the network lifetime is extended by our routing algorithm, which aims at minimizing the energy consumption of the target nodes rather than the entire network nodes. The results shows a 10% improvement on network lifetime. For EHWSN, the network throughput is increased by a predictable energy-efficient routing algorithm, which considering the harvested energy in the near future. The results demonstrate that the both network throughput and lifetime are increased. Show less

Date Issued

2016

Identifier

FSU_FA2016_Dong_fsu_0071E_13219

Format

Thesis

Title

Evaluation and DSP Based Implementation of PWM Approaches for Single-Phase DC-AC Converters.

Switching-mode single-phase DC-AC converters have been widely used in critical applications such as uninterrupted power supply systems and AC motor drivers. Among various control techniques, Pulse Width Modulation (PWM) technique is the most effective one that is commonly used to regulate the magnitude and frequency of the converter's output voltage. With recent revolution in the Digital Signal Processing (DSP) technology, the trend of converter control is moving to DSP based real-time... Show moreSwitching-mode single-phase DC-AC converters have been widely used in critical applications such as uninterrupted power supply systems and AC motor drivers. Among various control techniques, Pulse Width Modulation (PWM) technique is the most effective one that is commonly used to regulate the magnitude and frequency of the converter's output voltage. With recent revolution in the Digital Signal Processing (DSP) technology, the trend of converter control is moving to DSP based real-time digital control system. Digital control has the advantage of low cost with increased flexibility and accuracy. In this thesis, three open-loop PWM control schemes are evaluated and compared in both time domain and frequency domain. Theoretical analysis and spectrum evaluation have been completed. Digital simulation is conducted for each of the control schemes to verify the theoretical analysis. Experimental implementation based on a TMS320F2812 DSP is presented and finally system experimental results are demonstrated. Show less

Date Issued

2005

Identifier

FSU_migr_etd-0519

Format

Thesis

Title

Evaluation of a Benchmark Suite Exposing Android System Complexities Using Region-Based Caching.

The computer architecture community relies on standard benchmark suites like MiBench, NAS, PARSEC, SPEC CPU2006 (SPEC)®, and SPLASH to study different hardware designs, but such suites are insufficient for evaluating mobile platforms like Android. Even suites that were developed for embedded systems cannot be used to gain an understanding of Android device/system interaction because they do not exercise key components of the software stack. Although based on a conventional Linux ® kernel,... Show moreThe computer architecture community relies on standard benchmark suites like MiBench, NAS, PARSEC, SPEC CPU2006 (SPEC)®, and SPLASH to study different hardware designs, but such suites are insufficient for evaluating mobile platforms like Android. Even suites that were developed for embedded systems cannot be used to gain an understanding of Android device/system interaction because they do not exercise key components of the software stack. Although based on a conventional Linux ® kernel, Android includes native libraries, a virtual machine runtime, and an application framework with multiple components for managing resources. All these interact in complex ways to support Android applications. C programs running on Linux have a relatively simple virtual memory organization, and most memory references come from the application code. In contrast, Android has a much more complex virtual memory organization (due to its multiple APIs and numerous shared libraries), and most memory references come from the Android software stack. The complexity of Android's execution environment provides opportunities for computer architects to better support the execution characteristics, structures, and resource requirements of the Android software stack and opportunities for software developers to optimize their applications for this rich environment. To help the community to exploit these opportunities, we introduce Agave, an open-source benchmark suite designed to expose the complex interactions between components of the Android software stack. Show less

Date Issued

2016

Identifier

FSU_FA2016_Brown_fsu_0071E_13594

Format

Thesis

Title

Expansion and Implementation of the Wave Variable Method in Multiple Degree-of-Freedom Systems.

Adding force feedback to a teleoperation system can greatly improve a user's ability to complete tasks. However, operating in the presence of time delay can cause serious problems for bilateral teleoperation systems. Even a small amount of time delay in a bilateral teleoperation system will generally degrade the system's performance and can cause instability. An important approach that guarantees stability for any fixed time delay is the wave variable method. In this thesis some recent... Show moreAdding force feedback to a teleoperation system can greatly improve a user's ability to complete tasks. However, operating in the presence of time delay can cause serious problems for bilateral teleoperation systems. Even a small amount of time delay in a bilateral teleoperation system will generally degrade the system's performance and can cause instability. An important approach that guarantees stability for any fixed time delay is the wave variable method. In this thesis some recent material dealing with teleoperation systems using wave variables is presented. In particular, we describe a wave variable scheme based on a family of scaling matrices for a multiple degree-of-freedom bilateral teleoperation system. We include a derivation of a larger and more complete family of scaling matrices that will guarantee the system remains stable for a fixed time delay. The validity of the complete family of scaling matrices is verified through simulations and experiments. A multiple degree-of-freedom bilateral teleoperation system using the new wave variable method is simulated using a SIMULINK model. In addition, the new derivation was implemented in hardware using two different systems: an Immersion joystick with a C++ program and a PHANToM Omni haptic device with a virtual environment. Finally, an experiment was constructed using the PHANToM Omni haptic device as both the master and slave of the teleoperation system. Using Matlab and SIMULINK we added time delay to the communication channel and implemented the wave variable method with the complete family of scaling matrices. Human subjects were used to determine the best set of parameters for the system. Show less

Date Issued

2007

Identifier

FSU_migr_etd-0167

Format

Thesis

Title

Experimental and Mathematical Modeling Studies on Current Distribution in High Temperature Superconducting DC Cables.

High temperature superconducting power cables have the advantage of high current density and low losses over conventional cables. One of the factors that affect the stability and reliability of a superconducting cable is the distribution of current among the tapes of cable. Current distribution was investigated as a function of variations in contact resistance, individual tape critical current (Ic), and index (n)-value of individual tapes. It has been shown that besides contact resistances,... Show moreHigh temperature superconducting power cables have the advantage of high current density and low losses over conventional cables. One of the factors that affect the stability and reliability of a superconducting cable is the distribution of current among the tapes of cable. Current distribution was investigated as a function of variations in contact resistance, individual tape critical current (Ic), and index (n)-value of individual tapes. It has been shown that besides contact resistances, variations in other superconducting parameters affect current distribution. Variations in critical current and n-value become important at low contact resistances. The effects of collective variations in contact resistances, individual tape Ic, and n-values were studied through simulations using Monte Carlo method. Using an experimentally validated mathematical model, 1000 cables were simulated with normally distributed random values of contact resistances, individual tape Ics, and n-values. Current distribution in the 1000 simulated cables demonstrated the need for selecting tapes with a narrow distribution in the superconducting parameters to minimize the risk of catastrophic damage to superconducting cables during their operation. It has been demonstrated that there is a potential danger of pushing some tapes closer to their Ic before the current in the cable reaches its design critical current. Mathematical models were also used to study the effect of longitudinal variations in the tape parameters on superconducting cable using Monte Carlo simulations. Each tape of a 30 meter long, 3 kA model cable with 30 tapes was considered to have longitudinal variations in Ic, and n values for every 1 cm section, thus generating particular standard deviation in Ic and n for all 3000 sections of each tape. The results indicate that the apparent critical current and index value of the cable are reduced by a certain percentage depending upon the extent of variation in the characteristics along the length of the tapes. Show less

ABSTRACT A new type of hybrid hydrophobic/hydrophilic membrane is proposed in this thesis to improve the electrochemical performance of Lithium-Air battery operated with dual electrolytes. The dual electrolytes include an organic and aqueous electrolyte which is separated from one another by this solid-state hybrid polymer membrane so that they do not intermix. Also, this solid-state hybrid polymer membrane is conductive to facilitate the ionic charge carriers transport between the dual... Show moreABSTRACT A new type of hybrid hydrophobic/hydrophilic membrane is proposed in this thesis to improve the electrochemical performance of Lithium-Air battery operated with dual electrolytes. The dual electrolytes include an organic and aqueous electrolyte which is separated from one another by this solid-state hybrid polymer membrane so that they do not intermix. Also, this solid-state hybrid polymer membrane is conductive to facilitate the ionic charge carriers transport between the dual electrolytes. With polyvinylidene fluoride (PVDF) used as a hydrophobic polymer while polyvinyl alcohol (PVA) used as the hydrophilic polymer, the hybrid membranes were prepared by phase inversion and polymer solution casting processes to test the novel concept being proposed in this study. Moreover, the ionic conductivity, electrochemical stability, permeability, and morphology of the prepared PVDF/PVA hybrid membranes have been investigated to examine their suitability for Lithium-Air battery applications. The experimental results suggest that the PVDF/PVA hydrophobic/hydrophilic hybrid membrane is stable and potentially suitable to improve the performance of Lithium-Air battery operated with dual electrolytes. Show less

Date Issued

2012

Identifier

FSU_migr_etd-4686

Format

Thesis

Title

Fault Isolation in Power Electronic Based Distribution Systems without Circuit Breakers.

In the Future Renewable Electric Energy Distribution and Management (FREEDM) system, solid state Fault Isolation Devices (FIDs) are used to react to signals from a fault detection and location system to isolate faulted sections of a fault current limited power electronics based 12.47 kV distribution system. They accomplish this by interrupting fault currents, which in the FREEDM system are limited by Solid State Transformers (SST). However, as was expected, due to its silicon transistor... Show moreIn the Future Renewable Electric Energy Distribution and Management (FREEDM) system, solid state Fault Isolation Devices (FIDs) are used to react to signals from a fault detection and location system to isolate faulted sections of a fault current limited power electronics based 12.47 kV distribution system. They accomplish this by interrupting fault currents, which in the FREEDM system are limited by Solid State Transformers (SST). However, as was expected, due to its silicon transistor technology, the developed FID prototype demonstrated rather high on-state losses during its operation. Therefore, it is necessary to perform comparison studies with alternative methods of sectionalizing faulted parts of the FREEDM grid. To respond to this need, a system study has been undertaken to explore an alternative fault isolation strategy, which instead of allowing fault currents to remain in the system uses the abilities of the SSTs to completely turn off fault currents. Once this turn-off has been accomplished, regular mechanical disconnects isolate the faulted section and the system is reenergized. Behavioral 3-phase PSCAD average-value SST models have been developed and are used in a representative model of the FREEDM Green Hub to demonstrate how this strategy would operate. Simulation data is presented that shows how the SSTs would react to fault situations, remove fault currents, and reenergize the system. The characteristic example system was constructed and parameterized allowing for sensitivity analyses to be performed. A comparison is made with the fault-current-breaking FID method of fault isolation currently in use and it is discussed how the presented approach can be used to evaluate future FREEDM fault isolation strategies. Show less

Date Issued

2014

Identifier

FSU_migr_etd-8912

Format

Thesis

Title

Fault Protection Framework Designs and Methods in Power Electronics Converter Based Power Distribution Systems.

Due to technology development and continued increase in energy demand while keeping the environment protected, renewable resources started emerging rapidly within the distribution system. Renewable resources help to maintain power quality and reliability, but in high penetration, they can adversely affect the system operation by causing overvoltage issues or interfering with existing fault protection technologies. The existing fault protection methods do not always apply in these new... Show moreDue to technology development and continued increase in energy demand while keeping the environment protected, renewable resources started emerging rapidly within the distribution system. Renewable resources help to maintain power quality and reliability, but in high penetration, they can adversely affect the system operation by causing overvoltage issues or interfering with existing fault protection technologies. The existing fault protection methods do not always apply in these new distribution networks because of various reasons including cost, complexity of the system due to mesh-like network topology, presence of power electronics converters, and bidirectional power flow. In a system containing renewable resources, most fault protection technologies ignore the presence of the renewable resources by assuming either low penetration level or no power injection from renewable resources during a fault. The few fault protection technologies that consider the presence of renewable resources have not considered a network with power electronics (PE) converters that limit the fault current in the system. A fault protection system includes detection, location, and isolation of the faulted section and possible reconfiguration of the system. The work here is focused on fault detection and location because they present the challenging component of fault protection in a converter based distribution system with fault current limited. Isolation and reconfiguration are system dependent as they occur according to the physical arrangement of the system and the availability of resources. This thesis focuses on the design of a comparison framework which aims to help in choosing the most appropriate protection strategy for the system of interest. Because of the massive penetration of power electronics devices that interface with the renewable resources, the system of interest considered in this thesis is a fault current limited system. Considering the power rating, the line parameters, the converters, and the topology of the system, identify quantifiable characteristics of the system and derive a selection tree to help establish the most suitable protection scheme for the system. First, various meaningful influencing factors of existing fault protection detection and location are identified. In order to design a comparison framework, we consider the governing criteria for each protection scheme including some of the most common fault protection systems based on current only, voltage only, and current and voltage measurements. The sensitivity and selectivity of the protection scheme are also taken into consideration, and those characteristics are mapped to the current limiting system under study: the FREEDM system. "Smart Grid" concept is used to describe the idea of intelligently controlling renewable resources in the distribution system and all the other assets. Future Renewable Electric Energy Delivery and Management (FREEDM) system, which is one example of developing smart grid systems, is suitable for the study of the challenges related to fault protection technologies in a current limited system and the development of a fault location technology for significantly limited fault current system. Given the characteristics of the FREEDM system and the comparison framework developed, the differential pilot protection , the directional overcurrent protection , the directional overcurrent pilot section protection , and the voltage profile based protection3 were all chosen to be implemented on a fault current limited distribution system. The directional overcurrent pilot section protection was proposed to overcome the coordination issues that arise with the directional overcurrent protection therefore, making it faster. However, the small residual voltage remains a challenge for both directional protection technologies while the differential pilot protection is challenged by the large amount of measurements that need to be synchronized and processed. Thus, another fault location strategy is developed for converters based systems with fault current limited. This strategy takes advantage of the system topology, the presence of the controllable PE converters, and the change of the voltage profile with the presence of the fault. Show less